LakeSPI method summary

WHAT IS LakeSPI?

LakeSPI

Lake Submerged Plant Indicators (LakeSPI) is comprised of three indices: Native Condition Index, Invasive Impact Index and an overall LakeSPI Index.

Purpose

A survey method for the assessment of ecological condition of New Zealand lakes.

Biota Sampled

Submerged aquatic plants (macrophytes)

Underlying principles

A lake can be characterised by the composition of native and invasive plants and the depth to which they grow.

WHAT ARE THE USES OF LakeSPI?

Uses

To assess, monitor and report on lake ecological condition.

Application

To assist managers in assessing the effectiveness of management activities and to contribute to regional and national State of the Environment reporting requirements.

SURVEY PLANNING

Skills

Diving and basic plant identification

Equipment

Scuba diving equipment, boat (may be required), field gear (clipboard, pre-printed water proof sheets).

Lake Selection

Any lakes with submerged plants except where salinity, alkalinity, acidity, altitude or size prevents the development of normal submerged vegetation composition. It is not suitable for lakes where submerged plants are rare (i.e., site cover less than10%) or non-existent.

Site Selection

Sites affected by unfavourable influences such as stream inflows, steep gradients, exposed shorelines and disturbance areas (boat ramps and weed control areas) are avoided for the LakeSPI survey. Five survey sites are sufficient for most lakes.

Timing

Summer and autumn assessments are recommended. Frequency of survey will vary depending on management objectives, a lake's current condition and vulnerability to change.

HOW TO CARRY OUT A LakeSPI SURVEY

Field survey

This involves scuba diving at five representative sites within a lake and recording various components of native and invasive lake vegetation onto LakeSPI field sheets.

GENERATING LakeSPI SCORES AND INDICES

Site scores

Data captured on the site field sheet is used to generate three LakeSPI scores for an individual site. Separate native condition, invasive condition and LakeSPI scores are generated using scoring parameters, which relate to each vegetation feature being assessed.

LakeSPI indices

A mean of each of the final site scores for native condition, invasive condition and LakeSPI, are used to calculate the final indices: Native Condition Index, Invasive Impact Index, and overall LakeSPI Index. LakeSPI indices are expressed as a percentage of a lakes maximum scoring potential.

INTERPRETING RESULTS

Native Condition Index

This captures the native character of vegetation in a lake based on the biodiversity and extent of indigenous and native plant communities. A high 'native condition index' value will represent better lake condition.

Invasive Impact Index

This captures the invasive character of vegetation in a lake based on the degree of impact by invasive weed species. A high 'invasive condition index' value will represent poorer lake condition.

LakeSPI Index

This is a synthesis of components from both the native condition and invasive condition of a lake and provides an overall indication of a lake's ecological condition.

Lake comparisons

LakeSPI assesses and calculates LakeSPI indices based on a maximum potential score for each lake. This allows dissimilar lakes to be more directly compared.

Lake status

LakeSPI classifies lakes according to the value of their LakeSPI Index into 5 classes: Excellent, High, Moderate, Poor, Non-vegetated. This allows for lakes to be ranked within regions or nationally.